help truck is costing me an arm and a leg on fuel i have chenged fuel filter airfilter and checked air pressure i am lucky to get 10 mpg i used to get about 17 or so around town. i noticed it before the ulsd switch and it got alot worse with the new diesel so i started using bio from the sinclair station and its a little better but still not as much as it was about 6 months ago truck has 245,000 on it and has power runs good just terible milage

 

A good start

replace the overflow valve on the truck, if you havent already replace teh fuel filter canister, and im sure about the filter at the bottom of the truck, the prefilter, that probably hasnt been touched at all. The prefilter could use changing as well, U might also wanna check for fuel leaks... see if that gives...

Rick

 

Is the performance the same? It's not real likely, but the timing could have slipped, but if that was the case you would see a differnce driving the truck.

 

i agree with TXDiesel my truck got 9 mpg until i put a new prescreen filter and a overflow valve now it runs like a new one

 

my 97 CTD was leaking from fuel tank screw-on top. had to fab a long strap wrench to tighten.

when I'd fill up all the way, it'd leak a few gallons

 

I got terrible fuel economy with the ulsd also. but the guys are rite, prefilter and overflo valve are fairly cheep. also dont overlook any leaks

 

My mileage went from 17 to 10 once the ULSD hit the pumps. Dont know if this is ULSD itself, or the winter blend.

 

ULSD made me lose 1-2mpg and winter another 1-2. You seem to be losing alot more then that though. Can someone explain this pre filter and overflow valve to me a little more? might be something i should stock.

 

pre filter got changed no to long when i had to install an new lift pump also i have the screw on filter for the fuel nothing else to change there no fuel leaks put truck on lift at work to change the oil tonight and found no leaks well fuel anyway on the bottom or the top my tools to reset timing will be here tomrow so i will check that and restet the timing on saturday at the shop i need to check my vavle adjustment but i don't realy think that would cause a big loss in fuel milage

 

oh yes forgot my truck also has a clicking noise when it runs if i recall right couldn't the overflow vavle cause this?

 

Valve adjustment wouldn't cause that much of a drop. And your truck would not be running to well if the timing had slipped that much, I was just throwing that out there...

It looks like you need an overflow valve.

 

well i will order one when i get to work tomrow and put it in and see hopefuly thats all it is

 

my mileage for highway went from 22 down to 17 with new fuel.
last fillup with lots of in town mileage was the worst ever at 13

where's the overflow valve and pre-filter located?

 

Thanks to infidel for the pic of the overflow valve.



You may have to grind the notch a bit to get the old one out. Pretty simple job if you don't lose the washers. Takes about 5 minutes. Don't bend the line to get it out though, makes it terrible hard to get lined up again.

The prefilter is located inside the fuel preheater assembly. Look to the immediate left of the lift pump and you have the assembly. Takes a 17MM?? wrench to open it up (from the bottom) and the screen is inside.

 

Have you checked for boost leaks? Just a thought.